Electrical illuminating devices



April 30, 1957 K. L. BELL ELECTRICAL ILLUMINATING DEVICES Filed Jan. 18,1956 Q Q Q INVENTOR ATTORNEY man United States arent O i ELECTRICALILLUMINATING DEVICES Keith L. Bell, Washington, D. C., assignor to JamesAtkins, Arlington, Va., as trustee Application January-18,1956, SerialNo. 559,826

12 Claims. (Cl. 315-246) This invention relates to electricalilluminating devices and more particularly to illuminating devices usingradio frequency electrical energy as a source of power.

Various types of electro-luminescent cells are known in which visiblelight is produced by subjecting a phosphor coating to excitation by anelectrical field. All of the illuminating devices of this type of whichI am aware use exciting voltages at normal power frequencies. Radiofrequency voltages are capable of exciting phosphor materials to a muchgreater extent than the non-radiant energy of normal power frequencies.However, radio lfrequency voltages have not been used as a source ofexcitation energy in electro-luminescent devices due to the problemcreated of preventing undesirable radiation into space which wouldinterfere with radio and television reception.

Accordingly, it is an object of this invention to provide anilluminating device in which high frequency radiant energy is used as asource of activation or excitation for the phosphors or fluorescentmaterials which produce illumination.

It is another object of this invention to provide an illuminating devicein which a wave guide or coaxial cable serves as the envelope of theilluminating device.

I-t is still another object of this invention to provide an illuminatingdevice powered by radio frequency energy in such manner as not tointerfere with radio or television reception.

It is still another object of this invention to provide an illuminatingdevice in which the envelope of the illuminating device can be made muchlonger than is possible in the case ofrilluminating devices of the priorart.

In achievement of these objectives, there is provided in-accordance withan embodiment of this invention an illuminating device including a waveguide connected to a source of very high frequency radio energy. Thewave guide is formed of a material capable of light transmission, suchas glass, and is coated, preferably on its interior surface, with asuitable light transmissive or transparent conductive material to retainthe radio frequency energy within the interior of the wave guide. TheWave guide -is also coated on its interior surface with a suitablephosphor capable of emitting visible light rays when exposed to theradio frequency energy contained within the wave guide.

In a modified embodiment of the invention, a coaxial rcable is employedinstead of a wave guide. The coaxial cable is made of a material capableof light transmission and is provided with coatings of a light`transmissivev or transparent conductive material and of a phosphorsimilar to those used in the wave guide embodiment.

-Further -objects and advantages of the invention will become apparentfrom the following description taken in connection with the accompanyingdrawing in which:

Fig. l is -a view in longitudinal section, andpartially diagrammatic, ofan illuminating device in accordance `With the invention;-

12,790,936 Patented Apr. 30, 1,957

gig. 2 is a view in section along line 2 2 of Fig. 1; an

Fig. 3 is a view in longitudinal section, partially diagrammatic, of amodified illuminating device in accordance with the invention.

Referring now to the drawing, and more particularly to Fig. 1, there isshown an illuminating device generally indicated at 1t) including a waveguide generally indicated at 12 and a high frequency radio oscillatorgenerally indicated at 14 contained within a housing 16. Housing 16 isof metal or is otherwise suitably shielded to prevent radiation intospace of the radio frequency energy generated by the oscillator.Oscillator 14 is of a type capable of generating high frequency radiooscillations preferably in the centimeter wave length range.

Wave guide 12 which serves as the envelope for the illuminating device-is made of a material capable of light transmission, such as glass, ora light'transmissive plastic material, and is suitably joined at one kofits ends to housing 16 of oscillator 14 in a manner which insuresagainst any stray radiation at the junction between the wave guide andthe housing. The wave guide is closed at its outer end as indicated at17. The output circuit of oscillator 14 includes two conductors 18 and20 which are respectively connected to dipole members 22 and 24 whichextend into the end of Wave guide 12 adjacent the junction of the waveguide with the oscillator housing.

The wave guide is coated on its entire interior surface, including itslongitudinal wall surfaces and end wall surface, with a coating 26 of alight transmissive ortransparent electrically conductive material whichserves as a shielding means which retains the radio frequency energygenerated by oscillator 14 within the contines of the wave guide.

Light transmis-sive or transparent electrically conductive coating 26may be made of tin oxide or of other suitable materials, such as thosedescribed, for example, in U. S. Patent 2,648,754, entitledElectroconductive Article, issued to W. O. Lytle on August 11, 1953.

A coating 28 of a phosphor capable of emitting visible light rays whenexcited by radio frequency energy is deposited over the lighttransmissive or transparent electrically conductive coating 26. Coating28 thus lies inwardly of conductive coating 26 with respect to thelongitudinal axis of the wave guide. The phosphor material may be amixture containing parts of zinc sulphide and 25 parts of zinc oxide,with a small amount of an activator such as silver, copper or lead.Other phosphors may be used instead, such as sulphides of cadmium orcalcium, or zinc-cadmium sulphide phosphors, zinc-copper sulphidephosphors, or zinc-silicon-silver sulphide phosphors.

When oscillator 14 is energized, it propagates high frequency radiantenergy, preferably of the centimeter wave length range, into wave guide12. The radiant energy is confined within the wave guide due totransparent conductive coating 26. The radiant energy impinging upon thephosphor coating 28 causes the coating to luminesce, producing visiblelight rays. Since conductive Vcoating 26 and wave guide 12 are both madeof a light transmissive material the light rays are visible from theexterior of the wave guide, thereby causing the Wave guide to illuminatethe surrounding area.

There is shown in Fig. 3 a modified embodiment of the inventionoperating upon the same principle as the embodiment of Fig. 1. A coaxialcable generally indicated at 30 is formed of a lighttransmissivematerial, such as glass or a suitable plastic material, andis coated on its inner surface with a coating of alight transmissive ortransparent conductive material similar to that described in connectionwith the embodiment of Fig.r 1 and with a coating 34 of a phosphorsimilar to that described in conice ancona@ 3 nection Withthe.embodiment .of Fig.. 1. An end of .the coaxial cable 30 is connected toa metal or shielded housing 3,6 in which is `contained a highfrequencyradio oscillator generally indicated atBS. -One of the` output leads 40`of the oseillatoris connected tothe light transmissive or transparentconductive coating`32,-while the other outputlead 42 of the oscillatorris connected to the central conductor 44 of the coaxial cable. Centralconductor 44is insulatingly supported 4in `position-bythe spacedinsulating disks 46,in accordance with conventional practice in coaxialcables.

In order'to minimize power attentuation in the coaxial cable and toimprove the power factor of the apparatus, a terminating impedancergenerally indicated at IS-maybe connected at the end of the coaxialcable. The terminating impedance is positioned in a metal or shieldedhousing 50' which is connected to the end of the cable in a ,manner=which prevents stray radiation. The terminating impedance includes avariable condenser 52, a variable inductance 5d, and a variableresistance 56.

The operation of the embodiment of Fig. 3 as an illuminating device issimilar to that described in connection with the embodiment of Fig. l.When oscillator 36 is energized, it propagates high frequency radiantenergy into the coaxial cable. The radiant energy is confined within thecoaxial cable due to transparent conductive coating 32. The radiantenergy impinges upon the phos phor coating 34 and causes the coating toluminesce, producing visible light rays. Since conductive coating 32 andthe coaxial. cable are both made of a light transmissive material, thelight rays are visible from the exterior of the coaxial cable, causingthe coaxial cable to illumiv nate the surrounding area.

The cross sectional area of the wave guide 10 and of the coaxial cable30 should be proportioned relative to the wave length of the radiofrequency energy generated by the respective oscillators 14 and 38 inaccordance with the well known principles established for wave guidesand coaxial cables. (See Principles of Radar, M. I. T. Press,McGraw-Hill Book Co., 1952, page 546.) Or, conversely, to use a waveguide or coaxial cable of a predetermined desired diameter, the outputfrequency of the oscillator should be tixed at a value which produces awave length `consistent with the established relation betweenthe wavelength and the cross section of a wave guide or coaxial cable.

The illuminating devices hereinbefore described can i be used in anyinstallation requiring illumination, such as for residential use, forexample. However, it is believed that the devices of the invention haveparticular utility for illuminating large tioor areas, such as largeiioor areas in factories and the like. The wave guide and coaxial cablecan be made of considerable length, and a single length of wave guide orcoaxial cable can be bent into various desired conligurations. Also, aplurality of wave guides or coaxial cables may radiate like spokes of awheel from a central hubrwhich serves as a housing for an oscillatorwhich delivers radiant energy to all of the Wave guides or coaxialcables. In a still further modified arrangement, branch wave guidescommunicating with the interior of wave guide 10 may extendperpendicularly, or at other desired angles, from wave guide 10. Theradiant energy in wave guide l0 in such a modification passes to each ofthe communicating branch wave guides to excite phosphor' coatings in thebranch wave guides in the same manner as in the wave guide 10.

The operability of the embodiments of the invention as hereinbeforedescribed is independent of whether the interior of the envelope is atatmospheric pressure or under vacuum-conditions. The wave guide andcoaxial cable illuminating devices hereinbefore described are normallyoperated at atmospheric pressure and do not require hermetic sealing.Where desired, the light output of the device may be augmented bysealing into the interior-of when ionized. For example, CO2 (carbondioxide) may be sealed into the wave guide or coaxial cable at a reducedpressure of approximately 6 to 8 mm. of mercury. Car bon dioxide whenionized glows with a pure White light whose spectrum -is comparable tothat of sunlight. If a light output with an ultra-violet component isdesired, mercury may be placed on the interior of the wave guide orcoaxial cable either alone or in combination with the carbon dioxide.

it can be seen from the foregoing that there are provided in accordancewith this invention illuminating devices which have great utility inthat they permit the use of high frequency radiant energy as a source ofexcitation for phosphor materials in place of low frequency excitingvoltages, as heretofore practiced. The wave guide or coaxial 4cableilluminating devices hereinbefore described permit the use of radiofrequency exciting voltages for the phosphor materials Without anyundesirable radiation into space which would interfere with radio andtelevision reception. The devices of the invention permit the envelopeof the illuminating device to be much longer than in illuminatingdevices of the prior art, there by providing illuminating deviceswhichare particularly suitable for illuminating large tloor areas, such asfactory areas and the like.

While there have been shown and described particular embodiments of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from theinvention, and, therefore, it is aimed to cover all such changes andmodifications-as fall within the true spirit and scope ofthe invention.

vWhat I claim is:

l. An illuminating device comprising a closed light transmissiveenvelope, means for directing high frequency radiantenergy into theinterior of said envelope, light transmissive shielding means carried bysaid envelope for confining said radiant energy within said envelope,and a coating carried by said envelope and capable of emitting visiblelight when excited by said radiant energy.

2. An illuminating device comprising a closed light transmissiveenvelope, means for directing high frequency radiant energy into theinterior of said envelope, light transmissive shielding means carried bysaid envelope for contining said radiant energy within said envelope,and a phosphor coating carried by said envelope in overlying relation tosaid light transmissive shielding means and lying inwardly of saidshielding means with respect to the longitudinal axis of said envelope.

3. An illuminating device comprising a hollow Wave guide formed of lighttransmissive material, means for directing radiant energy into theinterior of said wave guide, light transmissive shielding means carriedby said wave guide for confining said radiant energy Within said waveguide, and a phosphor coating carried by said wave guide and capable ofemitting visible light when excited by said radiant energy.

4. An illuminating device comprising a coaxial cable formed of lighttransmissive materia-l, means for directing radiant energy into theinterior of said coaxial cable, light transmissive shielding meanscarried by said coaxial cable for confining said radiant energy Withinsaid coaxial cable, and a phosphor coating carried by said coaxial cableand capable of emitting visible light when excited yby said radiantenergy.

5. An illuminating device comprising a closed light transmissiveenvelope, means for directing high frequency radiant energy into theinterior of said envelope, a light transmissive electrically conductivecoating carried by said envelope for confining said radiant energywithin said envelope, and a phosphor coating carried by said envelopeand capable of emitting. visible light when excited by said radiantenergy.

6. An illuminating device comprising a closed light `transmissive hollowenvelope, means for directing high frequency radiant energy into theinterior of said envelope, said envelope having an electricallyconductive coating to confine said radiant energy Within said envelope,said envelope having a coating of a phosphor capable of emitting visiblelight when excited by said radiant energy, said phosphor coating lyinginwardly of said electrically conductive coating with respect to thelongitudinal axis of the envelope.

7. An illuminating device [comprising means for generating highfrequency radiant energy, a closed light transmissive envelopecommunicating with said means for receivinfT radiant energy from saidmeans, light transmissive shielding means carried by said envelope forconiining radiant energy within said envelope, and -a coating carried bysaid envelope and capable of emitting Visible llight when excited bysaid radiant energy.

8. An illuminating device comprising a radio oscillator capable ofgenerating high frequency radiant energy, a closed light transmissiveenvelope, the output of said oscillator extending into said envelope todirect radiant energy into `the interior thereof, light transmissiveshielding means carried by said envelope for confining said radiantenergy Within said envelope, and a phosphor coating carried by saidenvelope and capable of emitting visible light when excited by saidradiant energy.

9. An illuminating device comprising a radio oscillator capable ofgenerating high frequency radiant energy, a closed wave guide formed oflight transmissive material, lthe output of said oscillator extendinginto said wave guide to direct radiant energy into the interior thereof,a coating of light transmissive electrically conducting material carriedby said wave guide for confining said radiant energy within said waveguide, and a phosphor coating carried by said Wave guide injuxtaposition to said light transmissive conducting material and capableof emitting visible light when excited by said radiant energy.

l0. An illuminating device comprising a radio oscillator capable ofgenerating lhigh frequency radiant energy, a coaxial cable formed oflight transmissive material, the output of said oscillator extendinginto said coaxial cable to direct rad-iant energy into the interiorthereof, a coating of light transmissive electrically conductingmaterial carried by said coaxial cable for coniining said radiant energywithin said coaxial cable, and a phosphor coating carried by saidcoaxial cable in juxtaposition to said light transmissive conductingmaterial and capable of emitting visible light when excited by saidradiant energy.

1l. An illuminating device comprising a closed light transmissiveenvelope, means for directing high frequency radiant energy into `theinterior of said envelope, light transmissive shielding means carried bysaid envelope for confining said radiant energy within said envelope,and a gas conta-ined within said envelope capable of emitting visiblelight when subjected to the radiant energy Within said envelope.

l2. An illuminating device comprising a closed light transmissiveenvelope, means for directing high frequency radiant energy into theinterior of said envelope, light transmissive shielding means carried bysaid envelope for icom'ining said radiant energy within said envelope, agas contained Within said envelope capable of emitting visible lightwhen subjected to the radiant energy within said envelope, and aphosphor' coating carried by said envelope and capable of emittingvisible light when excited by said radiant energy.

No references cited.

